The North American and Pelican Nebulae I. IRAC Observations

TL;DR

This study maps the North American and Pelican Nebulae regions using Spitzer IRAC data, identifying over 1600 young stellar objects (YSOs) and analyzing their distribution, classes, and clustering to understand star formation in this region.

Contribution

First comprehensive IRAC-based survey of the North American and Pelican Nebulae, combining multi-wavelength data to identify and analyze YSO populations and their spatial distribution.

Findings

Most YSOs are Class II with a significant tail of Class I and flat spectrum objects.

YSOs are clustered, with about one-third in eight clusters near LDN 935.

Half of the YSOs are in regions with densities over 1000 YSOs/deg^2.

Abstract

We present a 9 deg^2 map of the North American and Pelican Nebulae regions obtained in all four IRAC channels with the Spitzer Space Telescope. The resulting photometry is merged with that at JHKs from 2MASS and a more spatially limited $BVI$ survey from previous ground-based work. We use a mixture of color- color diagrams to select a minimally contaminated set of more than 1600 objects that we claim are young stellar objects (YSOs) associated with the star forming region. Because our selection technique uses IR excess as a requirement, our sample is strongly biased against inclusion of Class III YSOs. The distribution of IRAC spectral slopes for our YSOs indicates that most of these objects are Class II, with a peak towards steeper spectral slopes but a substantial contribution from a tail of flat spectrum and Class I type objects. By studying the small fraction of the sample that is optically visible, we infer a typical age of a few Myr for the low mass population. The young stars are clustered, with about a third of them located in eight clusters that are located within or near the LDN 935 dark cloud. Half of the YSOs are located in regions with surface densities higher than 1000 YSOs / deg^2. The Class I objects are more clustered than the Class II stars.